To address the computational complexity of accurately calculating molecular absorption spectra in high?temperature environments and meet the demand for theoretical absorption spectrum calculations in broad?spectrum measurement fields, this study developed a precise and fast calculation model for molecular absorption spectra based on the High?Temperature molecular spectroscopic absorption parameters database (HITEMP). The model was implemented using Python language, employing a line?by?line calculation approach combined with simplification of line shape functions, line wing truncation criteria, and optimization of spectral line databases. The Hartmann?Tran line shape function was used as the standard absorption spectrum line shape, and partially?Correlated quadratic?Speed?Dependent Hard?Collision Profile (pCqSDHC) was developed for relevant second?order velocity?dependent hard?collision functions. By incorporating the Complex Probability Function (CPF) and simplifying the model, the line shape functions were calculated accurately and rapidly, resulting in a 20?fold increase in computational speed compared to theoretical models. The line wing truncation criteria were determined based on the spectral calculation residual at the level of 10-5 and involved the truncation of fixed wavenumbers combined with equal multiple truncations of spectral line half widths. Spectral data for each temperature gradient of 100 K were selected using a threshold line intensity of 10-25?cm-1/(mol?cm-2) and integrated to create an optimized database. The absorption spectra of water molecules were calculated within the range of 6 500 ~ 8 000 cm-1 and compared with the simulation results from "SpectraPlot.com", a molecular gas integrated spectral modeling website. The calculation error of the line?by?line model was at the level of 10-7, while the optimized model achieved a calculation error at the level of 10-5, with an average speed improvement of 25 times. This model enables efficient and accurate calculation of theoretical absorption spectra for absorption spectral measurements and provides a theoretical foundation for measuring studies based on wide?tunable and supercontinuum laser absorption spectra in complex environments.